The first atomic bomb created ‘forbidden’ quasicrystal

https://www.discovermagazine.com/the-sciences/the-first-atomic-bomb-created-this-forbidden-quasicrystal

by danboarder • 5 years ago

104 41 5 years ago

namelosw• 5 years ago

I just happened to come across this fascinating video[0] yesterday that explained the same thing. And he mentioned the crystal as well.

[0] The Infinite Pattern That Never Repeats: https://youtu.be/48sCx-wBs34

belter2• 5 years ago

Great video thanks for sharing. My brain still hurting, it tried to explode at 14.38 :-)

https://youtu.be/48sCx-wBs34?t=878

Also quite interesting these are found in a few meteorites. I wonder if somebody is confidentially keeping some quasicrystal with very special properties somewhere.

"Third-ever natural quasicrystal found in Siberian meteorite"

https://www.newscientist.com/article/2115570-third-ever-natu...

belter2• 5 years ago

It seems many here did not like the fact I did not know and find completely obvious, the fact that a Fibonacci sequence is a fundamental example of a 1D quasiperiodic structure exhibiting aperiodic long range order :-))

throwawaysea• 5 years ago

The article concludes by suggesting that people will create more quasicrystals in labs, with various desired properties. That seems reasonable. What I didn’t understand is this line:

And the more mathematically perfect they are, the less electrically conductive.

Anyone understand what “mathematically perfect” means here, or why that implies reduced conductivity?

mastazi2• 5 years ago

I'm not sure if my guess is right but my understanding is that "mathematically perfect" is related to how close to actual crystals they are. For example the Penrose tiling in the picture is made of tiles of 2 different types, so it's more "perfect" than another pattern that would use 3 different types of tiles, etc.

nleconte3• 5 years ago

I would have imagined it is used in the same way it is used for crystals. Mono-crystals are considered mathematically perfect, while poly-crystals (with their grain-boundaries separating different cyrstal orientations) are less perfect. So, for quasi-crystal, the patterning which follows a set of mathematical rules (although lacking translational invariance), can be interrupted, thus being "mathematically less perfect".

Now as to why that implied reduced conductivity... thinking in terms of Bloch waves, they require periodicity. In absence of Bloch waves that describe the electron density probability, the electrons are considered to be localized (e.g. as in the Landau level description of electrons implying localization of electrons in a perfect crystal). So for perfect quasi-crystals, this periodicity is fully absent, thus they are localized too. The latter hand-wavy argument is just speculation of mine...

mastazi2• 5 years ago

Wow this seems to be a very exciting research field:

Although more than 100 types of quasicrystals have been discovered since 1984, Steinhardt says that an infinite number of possibilities may exist — each with their own elastic, electronic, and photonic properties tied to the periodic ordering of their atoms.
Steinhardt’s own research group has worked to create “photonic quasicrystals,” which act as semiconductors for light and form nearly perfect spherical symmetric band gaps. That feature is desirable in circuit designs and could be used in future computer and communication devices.

senectus1• 5 years ago

I would imagine that once you start blowing stuff up in zero G you'll get even more interesting results.

ie: https://en.wikipedia.org/wiki/Widmanst%C3%A4tten_pattern

nleconte3• 5 years ago

A recent playfield for quasi-crystals have bee realized by making 30 degree twisted bilayer graphene. This playfield has been extended as well using stackings of any 2 different moire systems into one, with a 30 degree misalignmnent between the respective moire angles.

bedobi• 5 years ago

Are you sure? My understanding was that perturbations resulting from subatomic crevasses in multi-dimensional lattices would render the impedance greater than the Yui-Schwarz limit.

BizarroLand• 5 years ago

This made me visualize the periodic table of elements as a 3d stack of cubes, with a cross section of properties conferred by making various crystals out of the pure elements.

l33tman• 5 years ago

As a complete tangent, I recently heard a podcast [1] with Frank Wilczek, inventor of so called time-crystals, where he discussed materials where waves can propagate according to a rich enough set of rules to essentially "simulate" another world with its own set of physics. Fascinating.

[1] https://youtu.be/0zAlEjFU7xo?t=3000

eequah9L2• 5 years ago

quasicrystal materialized in temperatures above 2700 degrees Fahrenheit and pressures of 5000 to 8000 pascals. To you and me, it would feel similar to [...] someone carrying thousands of elephants [...] stands on your back.

Hmm, from my mechanical engineering times, 8 kP does not sound like a big deal at all.

Say it's 5 tons per elephant, which would be about 50kN. A human foot is about 25 cm long, and I guess two of them might be about as wide, so 0.0625 m^2. Pressure is force over area, so 800 kN/m^2, or 800 kP. That's per elephant.

I'm going to assume the article is missing a "mega" somewhere in there.

contravariant2• 5 years ago

Given that atmospheric pressure is around 100,000 pascals, yeah they're probably missing some SI prefix.

Edit: The original article talks about pressures of 5 to 8 GPa. [1]

[1] https://paulsteinhardt.org/wp-content/uploads/2021/05/BindiE...

hexo• 5 years ago

Reading those Fahrenheits and pascals in one sentence really hurts.

richrichardsson2• 5 years ago

For anyone not in USA (or the tiny handful of other countries still using it), Fahrenheit hurts to read full stop.

sandworm1013• 5 years ago

Temperature doesn't really exist. It is a concept for describing the kinetic energy of molecules. So we could go with some combination of meters/seconds/mass/atomic mass. We could call it the ped-kelvin, the temperature scale only used by the most pedantic of scientists.

ralabaster• 5 years ago

Oh, so now they’re ‘forbidden’? A few months ago they were only ‘impossible’.[1] I saved the article (which also was here on HN) at the time because it contains the conceit “science does what puny humans say is impossible,” but the people who say things are impossible are scientists themselves. Are we supposed to be impressed by that? Plagiarists, AKA journalists, get paid to copy other people’s work. Come to think of it, that’s what Stack Exchange is for, too…

[1]https://www.nature.com/articles/d41586-021-01332-0

craftinator2• 5 years ago

Much like the Colonel's 11 Secret Herbs and Spices, they are both Forbidden to know, and Impossible to understand.

egberts2• 5 years ago

What would be most interesting about these quasicrystal characteristics are: 1. tensile strength 2. cleaving strength 3. torsional strength

We have got starships to make that need to handle these upcoming warp engines.

Just looking ahead here.

Nbox9• 5 years ago

I am not a physicists.

I wonder if those properties would not be uniform across the quasicrystal because of it’s non-repeating pattern.

woah• 5 years ago

To you and me, it would feel similar to lying inside a volcano while someone carrying thousands of elephants (presumably stacked vertically) stands on your back.

Finally, a journalist using units of measurement I can relate to.

The first atomic bomb created ‘forbidden’ quasicrystal

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